1. Field of the Invention
This invention pertains to cutting tools, particularly hole cutting tools, and with greater particularity, hole cutting tools for cutting round or irregular holes by starting the cut in the center of the hole.
2. Description of the Prior Art
Modern materials have led to the development of a variety of tools to cut such material. Such tools include: cutting torches or arcs; lasers; and water jet cutting apparatus. All of these tools are distinguished by the fact that they cut at one point and are moved during operation to cut a line or profile.
It is often desirable to cut large diameter holes or cutouts in sheets of material. If the hole is larger than the diameter of the cut made by the tool, the tool must be moved to produce the outline of the hole. Three basic methods are used presently to accomplish this movement. First, the tool may be manually moved to follow an outline on the workpiece. This method has the advantage of simplicity, but the disadvantage that high tolerance cannot be duplicated. A second method is to move the tool around a template or form. This method has the advantage of greater reproducibility at the expense of added complexity and preparation costs for the templates. The third method is to provide motor drives in the x and y directions and link the drives to a computer or robot. This method provides excellent reproducibility and flexibility at a greatly increased cost.
With the cutting tools described, it is desirable to begin cutting at the center of the hole. The initial start up of the tool can lead to an increased kerf size at the start point, in the case of lasers or torches. With water jets cutting laminated materials, the start up torch can cause a point of delamination. If the tool is started on the edge of the hole sought to be made, therefore, the hole will either be irregular or contain a deliminated portion. For the above reasons, it is desirable to begin the cut at the center or discarded portion of the hole.
Of the methods described above, only the first and last is capable of beginning at the center of the hole. Such a process could be programmed into a computer or robot at additional expense, or done by hand. It is, therefore, desirable to produce a simple method for producing holes of large size, or irregular shape by use of a cutting tool that starts the cut at the center.